1. Field of the Invention
The invention relates to filters for use in pressure vessels.
2. Description of the Related Art
The use of filter bags in pressured vessels is known in the art. The purpose of the filter bag is remove contaminants from the various fluids that are poured through them. Each design has attempted to provide a low cost, highly efficient filter that can be easily changed. The major obstacle that has not been overcome is to provide a low cost method of ensuring that substantially all of the liquid goes through the filter without bypassing it because of an imperfect seal.
U.S. Pat. No. 4,202,966, issued to Morgan on May 27, 1980, discloses a filter element that is claimed to provide a hermetic seal between the filter and the pressure vessel that contains it. Tests by the inventor on PolyLoc.RTM., a filter element based on the teaching of this patent reveal substantial liquid is able to bypass the filter element under simulated operating conditions.
Similar tests conducted on other commercially available filter elements also reveal that substantial levels of liquid are able to bypass the filter element under simulated operating conditions.
Indeed, as far back as 1929, McGonigal, in U.S. Pat. No. 1,782,500, sought to solve the problem of easily changing filter elements yet providing a leak-proof seal. This design features an elaborate retaining mechanism that is impractical for today's filter needs.
U.S. Pat. No. 3,931,015, issued to Jenkins on Jan. 6, 1976, uses a filter element design that incorporates the use of the pressure vessel cap as a means to attempt a tight seal so that all the liquid will pass through the filter element.
Another attempt, U.S. Pat. No. 4,081,379, issued to Smith on Mar. 28, 1978, discloses the use of a complex multi-faceted filter bag being positioned between two parallel surfaces with a single sealing arrangement.
U.S. Pat. Nos. 3,959,137; 732,659; 2,191,395; 3,935,112; 3,651,947 and U.K Patent No. 242,082 disclose other designs for filter elements and are of general interest to the application.
Prior art filter elements have not met the need for a low cost, easily changed filter element that prevents unfiltered liquid from exiting the system.